This invention relates to an actuator for an accumulator type fuel injection nozzle and more particularly to improved actuator structure that permits better control over the fuel injection delivery.
A well known and popular type of fuel injector is the so-called accumulator type. With this type of fuel injection system, there is provided an accumulator chamber which is charged with fuel under pressure. The flow controlling discharge valve of the nozzle has an actuator that is mounted in a small control chamber that is also pressurized with fuel under pressure. When it is desired to inject fuel, the pressure in the control chamber is rapidly reduced by opening a relief valve for that chamber and the pressure in the accumulator chamber opens the injection valve and permits the fuel to be discharged.
One common type of system for actuating the relief valve includes an electromagnet that biases the relief valve to one of its positions, normally the open one, when energized so as to effect the fuel injection. Although such arrangements have particular utility, they make it difficult to control the actual amount of the fuel injected and the timing of the opening and closing of the injection valve.
It is, therefore, a principal object of this invention to provide an improved electromagnet arrangement for an accumulator type fuel injection nozzle.
It is a further object of this invention to provide an electromagnet assembly for operating an accumulator type fuel injection valve and wherein the operation of the electromagnet can be easily tuned to provide the desired flow conditions.
In conjunction with the use of such electromagnetically controlled fuel injection nozzles, it is important to insure that the device will be relatively temperature insensitive. This is particularly true when a resistor is utilized in the circuit for energizing the electromagnet to alter its performance.
It is, therefore, a still further object of this invention to provide an improved electromagnet control for a fuel injection nozzle that incorporates a temperature compensation system.
In connection with nozzles of this type, it is normally the practice to utilize only a single electromagnet that operates the relief valve in one direction, normally the opening direction. When a single electromagnet is employed, it is necessary to energize the magnet during the entire time that fuel is being discharged. This requires relatively high current loadings for fairly extensive periods of time. As a result, it is necessary to employ fairly substantially sized coils in order to provide the necessary force for holding the valve open for such long periods of time.
It is, therefore, a still further object of this invention to provide an improved arrangement wherein the coil size for the energizing the relief valve can be minimized.
It is a further object of this invention to provide an arrangement wherein separate coils are provided for both opening and closing the relief valve of an accumulator type fuel injection nozzle.